Biphenyldimethyldicarboxylate (BDD), a synthetic derivative of Schizandrin C which is one of the active ingredients isolated from Schizandra chinensis, has been known to lower the SGPT (serum glutamic pyruvic transaminase) level of a patient administered therewith, and accordingly, it is useful for treating liver diseases including acute/chronic viral hepatitis, a chronic liver disease and liver impairment by drug toxicity. (see [H. S. Lee, M. D., Y T. Kim, M. D. et al., “Prospective, randomized, controlled trial with biphenyl-dimethyl-dicarboxylate in chronic active liver diseases; The effect on lowering serum alanine aminotransferase levels, Dept. Of Internal Medicine and Liver Research Institute, Seoul Nat'l Univ. College Of Medicine, Seoul, Korea]).
Further, silybin, the primary component of a Carduus marianusextract, is known to have excellent activity in protecting liver cells from harmful effects caused by smoking, drinking, overworking, environmental contaminants, stress or liver-damaging drugs, and regenerating the liver cells. However, the bioavailability of orally administered BDD or silybin is unsatisfactorily low due to their low solubilities in water.
Liver diseases are caused mostly by a combination of many different factors, and therefore, a satisfactory therapeutic result cannot be obtained when a drug having a certain working mechanism is used alone. Nevertheless, the administration of a combination of two or more drugs may give rise to an undesirable side effect or antagonism induced by physical or chemical interactions between the drugs.
Accordingly, there has existed a need to develop an improved oral composition for treating liver diseases, which comprises two or more kinds of drugs having entirely different working mechanisms, has high in vivo bioavailabilities of the drugs, and causes no harmful side effects.